Techniques for transmitting and/or receiving an optical signal

Abstract

According to a first aspect of the present invention, there is provided a method for transmitting and/or receiving an optical signal through a fluid, the method comprising: using a pressure wave to cause a change in refractive index in the fluid, the change in refractive index causing a waveguide to be formed; and transmitting and/or receiving the optical signal through the waveguide.

The invention claimed is: 
     
       1. A method for transmitting and/or receiving an optical signal through a fluid, the method comprising:
 using a pressure wave to cause a change in refractive index in the fluid, the change in refractive index causing a waveguide to be formed; and 
 transmitting and/or receiving the optical signal through the waveguide; 
 wherein the waveguide is formed between a source of the optical signal and a receiver of the optical signal, and the optical signal propagates along a length of the waveguide between the source and the receiver. 
 
     
     
       2. The method of  claim 1 , wherein the change in refractive index is an increase in refractive index sufficient to achieve total internal reflection of the optical signal within the waveguide. 
     
     
       3. The method of  claim 1 , wherein the fluid is a liquid. 
     
     
       4. The method of  claim 1 , wherein the pressure wave takes the form of a Bessel-like beam, and the waveguide is formed within the Bessel-like beam. 
     
     
       5. The method of  claim 4 , wherein the waveguide is formed in a central lobe of the Bessel-like beam. 
     
     
       6. The method of  claim 1 , wherein the pressure wave takes the form of a standing wave, and the waveguide is formed within the standing wave. 
     
     
       7. The method of  claim 6 , wherein the waveguide is formed between an origin of the standing wave and a first node of the standing wave. 
     
     
       8. The method of  claim 7 , wherein an acoustic mirror is used to form the standing wave, the acoustic mirror being located at the first node of the standing wave. 
     
     
       9. The method of  claim 1 , wherein a transducer system comprising one or more transducers is used to generate the pressure wave. 
     
     
       10. The method of  claim 9 , wherein the transducer system comprising an annular array of transducers is used to generate the pressure wave. 
     
     
       11. The method of  claim 9 , wherein the transducer system comprises: a transducer; and an acoustic impedance matching layer for the transducer, for matching the acoustic impedance of the transducer with the acoustic impedance of the fluid. 
     
     
       12. The method of  claim 1 , wherein a laser is used to generate and/or transmit the optical signal. 
     
     
       13. The method of  claim 1 , wherein the method comprises:
 sensing a distance between the source of the optical signal and the receiver of the optical signal; and 
 one or both of generating the pressure wave and/or transmitting the optical signal only when the sensed optical distance is equal to or less than a threshold distance. 
 
     
     
       14. The method of  claim 1 , wherein the method comprises:
 sensing a distance between the source of the optical signal and the receiver of the optical signal; and 
 changing a property of the pressure wave to maintain or improve the transmission and/or reception of the optical signal based on the sensed distance. 
 
     
     
       15. A system for transmitting and/or receiving an optical signal through a fluid, the system comprising:
 a transducer system, arranged to generate a pressure wave in the fluid to cause a change in refractive index in the fluid, the change in refractive index causing a waveguide to be formed; and 
 a first optical transmitter or receiver, arranged to transmit or receive the optical signal through the waveguide; 
 wherein the waveguide is formed between the first optical transmitter or receiver and a second optical transmitter or receiver, and the optical signal propagates along a length of the waveguide between the first optical transmitter or receiver and the second optical transmitter or receiver. 
 
     
     
       16. The system of  claim 15 , wherein the change in refractive index is an increase in refractive index sufficient to achieve total internal reflection of the optical signal within the waveguide. 
     
     
       17. The system of  claim 15 , wherein the pressure wave takes the form of:
 a Bessel-like beam, and the waveguide is formed within the Bessel-like beam; or 
 a standing wave, and the waveguide is formed within the standing wave. 
 
     
     
       18. A system for transmitting an optical signal through a fluid, the system comprising:
 an array or transducers arranged to generate a pressure wave in the fluid to cause a change in refractive index in the fluid, the change in refractive index causing a waveguide to be formed in the fluid, wherein the optical signal is transmitted through the waveguide, wherein the waveguide is formed between a source of the optical signal and a receiver of the optical signal; and 
 an aperture through which the optical signal passes into the waveguide. 
 
     
     
       19. The system of  claim 18 , wherein the array or transducers is an annular array or transducers, and the aperture is located within the annular array. 
     
     
       20. The system of  claim 18 , wherein in addition to generating the pressure wave, the array of transducers is arranged to both generate and detect an acoustic signal that is used for a distance determination, the distance determination to determine a distance between an optical transmitter of the optical signal and a remote optical receiver of the optical signal, wherein the determined optical distance is used to determine at least property of the pressure wave.